<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        body{
            margin: 0;
            padding: 0;
            background: url(./images/bg.jpg);
        }
        .layer{
            position: fixed;
            left: 0;
            right: 0;
            top: 0;
            bottom: 0;
            /*background-color: rgba(0, 0, 0, 0.3);*/
            background-color: hsla(0, 10%, 10%, 0.8);
            /*opacity: 0.5;*/
            /*width: 100%;*/
            /*height: 100%;*/
        }
    </style>
</head>
<body>
    <div class="layer">
             <img src="./images/layer.jpg" alt="">
    </div>
</body>
</html>